CERTIFICATES OF COMPETENCY IN THE MERCHANT … · With reference to steam turbine ... preference to shrouding in the last few stages of the low pressure turbine ... a sketch of a

EXAMINATIONS ADMINISTERED BY THE SCOTTISH QUALIFICATIONS AUTHORITY

ON BEHALF OF MARITIME AND COASTGUARD AGENCY

CHIEF ENGINEER (UNLIMITED)

041-37 - ENGINEERING KNOWLEDGE - STEAM

WEDNESDAY, 17 December 2014

0915-1215 hrs

Examination paper inserts:

Notes for the guidance of candidates:

Materials to be supplied by examination centres:

CERTIFICATES OF COMPETENCY IN THE MERCHANT NAVY - MARINE ENGINEER OFFICER

Candidate's examination workbook

ENGINEERING KNOWLEDGE - STEAM

Attempt SIX questions onlyMarks for each part question are shown in brackets

1. (a) Explain how an assessment of combustion efficiency in boiler furnaces can be obtained from combustion gas analysis, making reference to the stoichiometric air-fuel ratio. (8)

(b) Explain how large, roof fired furnaces can improve the combustion process. (4)

(c) Explain why it is difficult to maintain a fixed air/fuel ratio over the boiler load range. (4)

2. With reference to a high pressure steam plant:

(a) state which gases may be present in the feed system, explaining their presence and their effect; (8)

(b) explain how the plant is protected from the undesirable effects of the gases stated in part (a). (8)

3. (a) Explain why ligament cracking between generating tube holes in a main boiler drum occasionally occurs. (6)

(b) Explain to what extent ligament cracking is considered serious, explaining how it may be dealt with. (10)

4. With reference to main boiler economisers, explain EACH of the following:

(a) the role of the economiser, and its limitations, in the efficiency of the steam plant; (6)

(b) how the operation and maintenance varies when the boiler is fired on residual fuel compared to natural gas. (10)

5. With reference to safety valves, explain EACH of the following:

(a) why the working lift may be as litle as one twenty-fourth of the valve diameter and yet the minimum mechanical lift must be a quarter of the diameter; (8)

(b) why a nozzle shaped seat may be used; (4)

(c) why a thermo-disc valve lid features in some designs. (4)

6. With reference to the horizontal flange joint on main turbines:

(a) describe, with the aid of sketches, a method of tightening main turbine flange studs, and the sequence in which this may be carried out; (7)

(b) describe the possible reasons for deformation of the material in the flange area and any operational defects that may arise due to this deformation; (5)

(c) state the repairs that may be considered if leakage occurs across the flange joint. (4)

7. With reference to steam turbine blading, explain EACH of the following:

(a) the advantages of fitting blades into individual axial slots rather than a circumferential groove; (6)

(b) why lacing wires may be used in preference to shrouding in the last few stages of the low pressure turbine; (6)

(c) the advantages of integral shrouding. (4)

8. With reference to extraction pumps fitted to dry bottomed condensers, explain EACH of the following:

(a) how cavitation is used to control the flow of condensate; (4)

(b) the problems designing such a pump; (4)

(c) how the glands are sealed; (4)

(d) the run of the pipework between the pump and condenser. (4)

9. On a routine gear inspection incipient pitting is noted on both the forward and after ends of the main gear wheel.

(a) Explain what is meant by incipient pitting and why this pitting occurs. (5)

(b) Describe how its cause could be determined. (6)

(c) Explain the remedial action to be taken. (5)





WEDNESDAY, 23 July 2014

0915-1215 hrs





Datasheet Q5




1. With reference to a main propulsion plant:

(a) explain the importance of maintaining the steam temperature at superheat outlet within close proximity to the maximum permissible temperature at that point; (2)

(b) discuss the immediate and long term effects of excursions of steam temperature above the permissible limit; (8)

(c) explain why it is preferable to pass all steam through the superheater rather than to draw dry saturated steam from the main steam drum. Give reasons for any exceptions. (6)

2. With reference to the safety valves on a high pressure boiler, explain EACH of the following:

(a) why a resilient lid may be fitted; (4)


(c) why safety valves are fitted on both steam drum and superheater; (4)

(d) why mechanical easing gear must be fitted. (4)

3. (a) Explain the causes of a boiler panting. (3)

(b) Explain the panting process. (7)

(c) State how a combustion control system reduces panting. (3)

(d) State the probable effects of allowing panting to continue unchecked. (3)

4. With reference to boiler and feed water, explain EACH of the following:

(a) why the testing for ammonia and silica has become routine, stating the permitted limits and the action taken if out of limits; (8)

(b) why the Co-ordinated Phosphate - pH form of boiler water treatment is used, describing the method of control; (5)

(c) why it may be difficult to maintain boiler water in the desired condition during manoeuvring. (3)

5. With reference to the gear tooth defects shown on the Datasheet, explain the cause of their occurrence and the remedial action to be taken in EACH of the following:

(a) illustration (a) on the Datasheet; (8)

(b) illustration (b) on the Datasheet; (4)

(c) illlustration (c) on the Datasheet. (4)

6. With reference to marine condenser tubes:

(a) explain the factors that govern the choice of tube diameter; (6)

(b) explain the suitability of the following materials and any protection measures which may be provided: cupro nickel; stainless steel; titanium. (10)



(b) why lacing wires may be used in preference to shrouding in the last few stages of the low pressure turbine' (5)


8. (a) Sketch a manoeuvring valve lid and seat, explaining how, whilst only a small effort is required to operate the valve, tight shut off is obtained. (12)

(b) Explain how the manoeuvring valve characteristics enable precise speed control at low powers. (4)

9. List SIX emergency trips fitted to a monoplanar cross compound turbine set, stating reasons for fitting EACH of them and explaining how EACH trip is ensured to be in working order. (16)





WEDNESDAY, 09 April 2014

0915-1215 hrs








1. Describe the pre-commissioning inspections, test and cleaning operations that should be carried out on a high pressure main boiler in a new vessel. (16)

2. Give a reasoned opinion as to the accuracy of EACH of the following statements regarding main boiler mountings:

(a) to protect a boiler superheater the steam loaded, full bore type of safety valve with a pilot valve on the drum, is preferable to the direct spring-loaded type; (6)

(b) drum mounted glass column boiler water level gauges are now redundant and only introduce an unnecessary hazard into the contempory machinery space environment; (6)

(c) scum dishes are no longer required in the steam drum. (4)

3. With reference to automatic combustion control, explain with the aid of a diagram:

(a) how steam pressure is maintained and emission of black smoke is prevented during rapid manoeuvring; (10)

(b) how air and fuel flow are measured and incorporated into the system. (6)

4. (a) State the possible reasons for EACH of the following changes in boiler water test results, stating the checks to be made in each case:

(i) reduction in total dissolved solids and chemical reserves; (3)

(ii) reduction in phosphate reserve with increase in chlorinity and total dissolved solids; (3)

(iii) reduction in alkalinity reserve only; (3)

(iv) increase in oxygen levels only. (4)

(b) Explain why the complete results of boiler tests are logged or entered into a data retrieval system rather than a note being made of any particular result which may be outside set limits. (3)

5. On a routine gear inspection incipient pitting is noticed on both the forward and after ends of the main gear wheel.

(a) Explain why this pitting occurs. (5)


(c) Explain how the defect may progress and the possible consequences. (5)

6. With reference to low pressure main turbines:

(a) explain why drainage is important in the latter stages; (3)

(b) describe how the blades in the final stages are protected against erosion; (4)

(c) indicate on a sketch of a blade where erosion is likely to occur, explaining why it occurs in that position; (5)

(d) state, with reasons, why shrouding may be omitted in the latter stages. (4)

7. With reference to main condensers:

(a) state the effects of exhaust steam encountering inadequate cooling surface; (2)

(b) explain why corrosion of tubes may occur in the air extraction sections; (3)

(c) describe the factors that influence the use of scoop circulation; (3)

(d) state THREE methods that may be employed in locating small sea water leaks; (3)

(e) describe ONE of the methods stated in part (d) identifying any difficulties that may be encountered and how these may be overcome. (5)

8. With reference to extraction pumps fitted to dry bottomed condensers, explain EACH of the following:

(a) how cavitation is used to control the flow of condensate; (4)

(b) the problems designing such a pump; (4)

(c) how the glands are sealed; (4)

(d) the run of the pipework between the pump and condenser. (4)

9. With reference to sequential opening of nozzle groups on a turbo-alternator:

(a) explain the advantages of this arrangement; (4)

(b) describe how it is achieved automatically; (6)

(c) explain the malfunctions that may occur and how they are rectified. (6)





WEDNESDAY, 11 December 2013

0915-1215 hrs








1. With reference to water tube boilers:

(a) explain the influence of water circulation upon steam generation; (4)

(b) state, with reasons, TWO operational conditions that would cause natural circulation to break down; (4)

(c) Explain how the design features of a boiler affect natural circulation. (8)

2. (a) Explain why deaerators are incorporated in closed feed systems despite the air ejector removing the incondensable gases from the main condenser. (5)

(b) Explain how deaerators contribute to the overall thermal efficiency of the plant, and comment on their position in the engine room. (6)

(c) Explain how in spite of incorporation of both air ejectors and deaerators, oxygen and carbon dioxide can still enter the main boilers. (5)

3. With reference to water conditioning, discuss the importance of EACH of the following:

(a) the nozzles fitted in a deaerator; (4)

(b) monitoring of pH level in the condensate in the main feed system; (4)

(c) boiler water sample coolers; (3)

(d) an ion exchange unit in the make-up feed line is an unnecessary complication. (5)

4. With reference to main turbine rotors:

(a) explain why they may be manufactured with an axial hole extending throughout their entire length; (4)

(b) state why various test pieces are taken from the rotor after forging; (4)

(c) explain the significance of the thermal stability test performed on some rotors; (4)

(d) explain why journal bearings have a length of less than their diameter. (4)

5. Explain how EACH of the following tooth faults in main gearing develops and is identified, outlining how the possibility of further damage may be reduced:

(a) interference wear; (5)

(b) pitting; (6)

(c) scuffing. (5)

6. Provide reasoned opinions as to the accuracy of EACH of the following:

(a) feed regulators operating solely by level sensing are incapable of conrolling the water level in a steam drum adequately; (6)

(b) drum mounted column water gauge glasses are now redundant and introduce an unnecessary hazard into the modern machinery space; (6)

(c) a viscotherm is an unnecessary complication in a fuel oil combustion system. (4)

7. With reference to the combustion of fuel oil in boilers, explain EACH of the following:

(a) the reasons for using a large furnace; (4)

(b) why it is difficult to maintain a fixed air/fuel ratio over the whole load range; (4)

(c) how the air/fuel ratio is finely adjusted when full away; (4)

(d) the benefits of using fuel oil additives, stating the reasons why they may not be used. (4)

8. As Chief Engineer Officer explain how the performance of the main steam turbines are monitored, even though the power and sea temperature differ from that on sea trials. (16)

9. With reference to auxiliary diesel engines, state the probable causes that would create EACH of the following conditions, explaining how they would be rectified:

(a) knocking; (6)

(b) loss of power; (6)

(c) loss of lubricating oil presssure. (4)





WEDNESDAY, 16 October 2013

0915-1215 hrs





Candidate’s examination workbook



1. With reference to a boiler fitted with an automatic combustion control system, list EACH of the following, explaining why EACH is fitted:

(a) FIVE permissive interlocks; (10)

(b) THREE shutdown interlocks. (6)

2. With reference to the safety valves on a high pressure boiler, explain EACH of the following:

(a) why a resilient valve lid is fitted; (4)


(c) why superheater safety valves are set to open at a lower pressure than valves on the main drum; (4)

(d) why mechanical easing gear must be fitted. (4)

3. With reference to steam sootblowers, explain EACH of the following:

(a) the factors that determine the frequency of operation; (5)

(b) the procedures before operation of sootblowers; (5)

(c) why the steam pipes in the sootblowing system can be more prone to corrosion than other steam pipes and how this may be minimised. (6)

4. A pressure differential must exist between the main feed pump and the boiler. Describe with the aid of head/flow diagrams, the characteristics associated with types of feed pump control regarding speed, pressure and flow over the full range of feed flow, commenting on complexity and economy. (16)

5. On a routine gear inspection incipient pitting is noted on both the forward and after ends of the main gear wheel.

(a) Explain what is meant by incipient pitting and why this pitting occurs. (5)


(c) Explain the remedial action to be taken. (5)

6. With reference to the main lubricating oil pump being driven directly by the main propulsion plant:

(a) state the advantages; (4)

(b) describe such a pump and drive; (8)

(c) explain how continuity of oil supply is achieved during manoeuvring. (4)

7. (a) Sketch a manoeuvring valve lid and seat, explaining how, whilst only a small effort is required to operate the valve, tight shut off is obtained. (12)

(b) Explain how the manoeuvring valve characteristics enable precise speed control at low powers. (4)

8. With reference to deaerators fitted in the feed system:

(a) explain why the accuracy of the pressure gauge and the thermometer fitted to the shell is important; (5)

(b) describe TWO designs whereby the effectiveness of the deaerator can be maintained over a wide range of load; (6)

(c) explain the advantages and disadvantages of returning the condensate from the devapouriser to the feed system. (5)

9. With reference to auxiliary diesel engines, explain EACH of the following:

(a) how piston ring breakage occurs; (5)

(b) how piston ring breakage can be avoided; (5)

(c) what effects face contouring, ring cross-section and the material properties of rings and liners have on ring life. (6)





WEDNESDAY, 17 July 2013

0915-1215 hrs








1. (a) Explain the factors that influence the choice of tube diameter in marine condensers and comment on the tube material and protection. (10)

(b) Explain how the following conditions associated with main condensers may be diagnosed:

(i) deposits on tube surfaces; (2)

(ii) faulty vacuum pump; (2)

(iii) blocked tubes. (2)

2. With reference to a full lift safety valve:

(a) describe the main features of such a valve, explaining the design principles; (12)

(b) state which clearances are important, explaining their significance in valve action. (4)

3. With reference to water tube boilers:

(a) explain the influence of water circulation upon steam generation; (4)

(b) state, with reasons, TWO operational conditions that would cause natural circulation to break down; (4)

(c) explain how the design features of a boiler affect natural circulation. (8)





(d) explain why journal bearings have a length of less than their diameter in modern practice. (4)

5. (a) With reference to the blades fitted in Low Pressure main turbines, explain EACH of the following:

(i) why casing drainage is important in the final stages; (4)

(ii) why it may be necessary to protect the blades fitted in the final ahead stages against erosion; (5)

(iii) why shrouding is sometimes omitted on the last few stages. (3)

(b) Explain why, when running in the ahead direction, the blading of the astern turbine might be subject to erosion, where on the blades this may occur, and possible means of prevention. (4)

6. (a) Explain the limitations of a boiler feed water regulator sensing water level alone. (6)

(b) Describe with the aid of a block diagram, a control system that overcomes the limitations explained in part (a). (10)

7. (a) State, with reasons, why the intermittent analysis and the slug injection of chemicals to a boiler may be considered inadequate. (4)

(b) Explain why certain results from boiler water tests may not be in keeping with chemical dosage under varying load conditions. (6)

(c) State why significant excess of sodium hydroxide in main boilers is to be discouraged. (6)

8. Describe how EACH of the following gear tooth defects is detected by visual inspection, explaining the causes of its occurrence and the remedial action to be taken:

(a) pitting on new gears after sea trials; (4)

(b) pitting on the ends of gear teeth after some years of satisfactory performance; (4)

(c) scoring; (3)

(d) scuffing; (3)

(e) rippling or fishscaling. (2)

9. With reference to a piston seizing in an auxiliary diesel engine:

(a) explain the problems that may occur during removal, if it is not possible to remove the piston from the liner; (6)

(b) state how the engine could be brought back into service; (6)

(c) explain the checks that it would be advisable to carry out on the rest of the engine. (4)





WEDNESDAY, 27 March 2013

0915-1215 hrs








Section A

1. (a) Explain why superheaters are used in conjunction with high pressure boilers, stating the factors limiting superheating. (4)

(b) Describe THREE methods of controlling superheat temperature, stating the effectiveness of EACH at maintaining the desired steam temperature. (12)

2. Explain the design requirements for the high pressure main boiler safety valves and associated pipework for the safe and economic operation of the ship. (16)

3. (a) Explain the limitations of a boiler feed water regulator sensing water level alone. (6)

(b) Describe with the aid of a block diagram, a control system that overcomes the limitations explained in part (a). (10)

4. With reference to carbon dioxide contamination of the steam and water side of steam plant, explain EACH of the following:

(a) the possible sources of contamination; (5)

(b) the effects of contamination; (5)

(c) how contamination may be combatted, stating any side effects. (6)





(d) explain why journal bearings have a length of less than their diameter in modern practice. (4)

6. Under Full Away conditions the vibration monitor on the low pressure turbine indicates excessive vibration:

(a) state the possible causes, explaining how, and in what sequence, they would be identified; (8)

(b) if the cause of excessive vibration was beyond shipboard repair, explain EACH of the following:

(i) how the ship could be steamed to the next port; (4)

(ii) how the voyage may be continued, with no consequential damage, if there is no repair facility at this port. (4)



(b) why lacing wires may be used in preference to shrouding in the last few stages of the low pressure turbine; (6)


8. With reference to main condensers, explain EACH of the following:

(a) how relative expansion of tubes and shell is accommodated; (4)

(b) why tube pitching may vary; (4)

(c) why tubes may occasionally fail in way of intermediate diaphragm plates; (4)

(d) how tube inlet wastage can be minimised. (4)

9. Describe how EACH of the following gear tooth defects is detected by visual inspection, explaining the causes of its occurrence and the remedial action to be taken:

(a) pitting on new gears after sea trials; (4)

(b) pitting on the ends of gear teeth after some years of satisfactory performance; (4)

(c) scoring; (3)

(d) scuffing; (3)

(e) rippling or fishscaling. (2)

CERTIFICATES OF COMPETENCY IN THE MERCHANT NAVY –

MARINE ENGINEER OFFICER

EXAMINATIONS ADMINISTERED BY THE

SCOTTISH QUALIFICATIONS AUTHORITY

ON BEHALF OF THE

MARITIME AND COASTGUARD AGENCY

STCW 95 CHIEF ENGINEER REG. III/2 (UNLIMITED)

041-37 – ENGINEERING KNOWLEDGE - STEAM

WEDNESDAY, 14 DECEMBER 2011

0915- 1215 hrs





[OVER

ENGINEERING KNOWLEDGE – STEAM

Attempt SIX questions only

All questions carry equal marks

Marks for each part question are shown in brackets

1. (a) Describe how a main boiler and economiser are secured to the ship’s structure,

explaining how the forces due to boiler deadweight and ship’s motion are transferred

to the hull.

(b) State the routine attention that should be given to boiler support arrangements.

(12)

(4)

2. With reference to boiler superheaters:

(a) explain how the tubes are supported in EACH of the following arrangements:

(i) vertical;

(ii) horizontal;

(b) state the advantages and disadvantages of EACH arrangement in Q2(a).

(5)

(5)

(6)

3. With reference to high pressure boilers, discuss the accuracy of EACH of the following

statements:

(a) accumulation of pressure does not occur when full lift safety valves operate;

(b) scum pans are an unnecessary fitting;

(c) feed check valves have been rendered redundant by multi element feed regulators.

(5)

(5)

(6)

4. (a) Describe the use of the Co-ordinated Phosphate – pH form of treatment for boiler

water, explaining the method of control.

(b) Explain why it is difficult to maintain the desirable boiler and feed water chemistry

during manoeuvring.

(c) Explain why an ammonia test may be required, quoting the permitted level and where

the sample is taken from.

(6)

(5)

(5)

5. With reference to the final stages of a low pressure propulsion turbine, explain EACH of

the following:

(a) why axial twist should be imparted to the blades;

(b) why the clearance between the nozzles and blades may vary over the length of the

blades;

(c) how this region of the turbine is protected from erosion.

(5)

(4)

(7)

6. With reference to labyrinth glands fitted to propulsion turbines:

(a) state the materials used, explaining why the choice may be limited;

(b) explain why spring backed segments are normally used;

(c) sketch a section through a segment that is pressure balanced, explaining the

advantages of this system.

(5)

(4)

(7)

7. With reference to main reduction gearing:

(a) explain, with the aid of sketches, where EACH of the following features are provided

and the purpose of EACH;

(i) end relief;

(ii) tip relief;

(b) explain the factors which determine the amount of backlash;

(c) explain why flexible couplings are fitted between primary and secondary gear

reductions.

(5)

(3)

(4)

(4)

8. With reference to lubricating oil in geared turbine propulsion plant, explain EACH of the

following:

(a) the problems that frothing causes;

(b) the operational measures that help prevent frothing;

(c) the design features that help prevent frothing.

(6)

(5)

(5)

9. With reference to turbo-alternator turbines and gearing, describe the safety devices fitted,

stating the potential consequences if not fitted.

(16)

CERTIFICATES OF COMPETENCY IN THE MERCHANT NAVY – MARINE ENGINEER OFFICER

EXAMINATIONS ADMINISTERED BY THE

SCOTTISH QUALIFICATIONS AUTHORITY ON BEHALF OF THE

MARITIME AND COASTGUARD AGENCY

STCW 95 CHIEF ENGINEER REG. III/2 (UNLIMITED)

041-37 – ENGINEERING KNOWLEDGE - STEAM

WEDNESDAY, 30 MARCH 2011 0915- 1215 hrs Examination paper inserts: Notes for the guidance of candidates:

Materials to be supplied by colleges:


[OVER

ENGINEERING KNOWLEDGE – STEAM Attempt SIX questions only All questions carry equal marks Marks for each part question are shown in brackets

1. With reference to water tube boilers: (a) discuss those factors that retard natural circulation resulting from design and

operation; (b) state reasons for the usual method of introducing feed water into the boiler,

explaining why it is not supplied directly to the water drum; (c) explain the conditions when reversed circulation may occur and the ensuing

danger.

(7)

(4)

(5)

2. (a) Describe the equipment that may be fitted to analyse flue gas so that the combustion efficiency can be assessed.

(b) Explain how the accuracy of flue gas analysing equipment may be checked.

(11)

(5)

3. With reference to the safety valves fitted to main boilers: (a) state, with reasons, the parts requiring particular attention during overhaul; (b) describe the setting of the valves after overhaul; (c) explain why the lifting of the valves under steam should be kept to a minimum.

(6)

(8)

(2)

4. With reference to iron oxides found on the waterside of boilers: (a) describe the forms in which they may be found, stating how they originate; (b) explain their beneficial and detrimental effects; (c) describe the operational practices that encourage the beneficial effect; (d) state what may cause a partial loss of the beneficial effect.

(5)

(4)

(5)

(2)

5. With reference to astern turbines: (a) sketch a cross section, from the last row of blades of the low pressure ahead

turbine to the exhaust end bearing; (b) state, with reasons, how it differs from the ahead turbines; (c) state the maximum power developed compared to the ahead turbines; (d) explain how windage losses are reduced.

(4)

(6)

(2)

(4)

6. Describe the periodic inspection of EACH of the following types of pipe, stating the defects that may be found and how the pipes are tested: (a) welded main steam pipe; (b) boiler blow down pipe; (c) safety valve waste steam pipe.

(6)

(5)

(5)

7. With reference to the horizontal joint in the casing of a high pressure turbine: (a) explain how flange warp occurs; (b) state the operating conditions that exacerbate the warping; (c) describe the actions that should be taken at various stages of warping.

(6)

(3)

(7)

8. With reference to main reduction gearing: (a) explain, with the aid of sketches, a modified addendum tooth profile compared to

standard involute profile, stating its benefit; (b) sketch where the pitch line occurs on the tooth profile, explaining the significance

of tooth contact along this line; (c) explain where EACH of the following is provided, stating the purpose of EACH;

(i) end relief; (ii) tip relief.

(5)

(3)

(5)

(3)

9. With reference to the bottom end bolts of auxiliary diesel engines; (a) explain why they are prone to failure; (b) state, with reasons, the inspection carried out to minimise the risk of failure; (c) describe how bolt design can reduce the risk of failure.

(5)

(6)

(5)

Documents

CERTIFICATES OF COMPETENCY IN THE MERCHANT … · With reference to steam turbine ... preference to shrouding in the last few stages of the low pressure turbine ... a sketch of a